|
 The data, which was published in the Lancet published medical
journal, had been previously released in August ahead of peer
review.
The analysis showed that the vaccine's effectiveness in preventing
hospitalization and death remained high at 90% for at least six
months, even against the highly contagious Delta variant of the
coronavirus.
The data suggests that the drop is due to waning efficacy, rather
than more contagious variants, researchers said.
Researchers from Pfizer and Kaiser Permanente studied electronic
health records of roughly 3.4 million people who were members of
Kaiser Permanente Southern California between December 2020 - when
the vaccine first became available - and August of 2021.
"Our variant-specific analysis clearly shows that the (Pfizer/BioNTech)
vaccine is effective against all current variants of concern,
including Delta," said Luis Jodar, senior vice president and chief
medical officer at Pfizer vaccines.
A potential limitation of the study was a lack of data on adherence
to masking guidelines and occupations in the study population, which
could have affected frequency of testing and likelihood of exposure
to the virus.
Vaccine effectiveness against the Delta variant was 93% after the
first month, declining to 53% after four months. Against other
coronavirus variants, efficacy declined to 67% from 97%.
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 "To us, that suggests Delta is
not an escape variant that is completely evading
vaccine protection," said study leader Sara
Tartof with Kaiser Permanente Southern
California's Department of Research &
Evaluation. "If it was, we would
probably not have seen high protection after vaccination, because
vaccination would not be working in that case. It would start low,
and stay low."
Testing for variants is more likely to fail in vaccinated
individuals, which could lead to overestimation of variant-specific
effectiveness in the study, the authors cautioned.
 The U.S. Food and Drug Administration has authorized the use of a
booster dose of the Pfizer/BioNTech vaccine for older adults and
some Americans at high-risk of getting infected. Scientists have
called for more data on whether boosters should be recommended for
all.
(Reporting by Manas Mishra in Bengaluru; Editing by Bill Berkrot)
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